Conventionally, there is used a spring-pressurizing unit in which a screw member having a shaft is allowed to stand like a pillar, and the member is pressed by a spring around the shaft.
FIG. 1 is a schematic diagram of a package unit having one example of such a spring-pressurizing unit.
The package unit 100 has such a structure that a semiconductor package 30 is mounted on a system board 10 by melting and fixing solder balls 20, and a cooling unit 50 is disposed on the semiconductor package 30 with a thermally bonding member 40 interposed therebetween. The cooling unit 50 includes a base body 51 and a large number of fins 52 standing on the base body 51. The base body 51 has a through hole 511 formed therein, which a columnar female screw member 61 passes through. A male screw member 62 stands on the system board 10. The female screw member 61 has a head 611 whose diameter is greater than that of the female screw member 61. The shaft of the female screw member 61 passes through a coil spring 63, and a shaft of the female screw member 61 passes through the through hole 511 of the base body 51 of the cooling unit 50. The coil spring 63 is sandwiched between the head 611 of the female screw member 61 and the base body 51 of the cooling unit 50, the coil spring 63 is screwed over the male screw member 62 and fastened. During this screwed state, the coil spring 63 is contracted between the head 611 and the base body 51, the cooling unit 50 is pressed toward the system board 10 by the coil spring 63, the cooling unit 50 comes into intimate contact with the semiconductor package 30 with the thermally bonding member 40 interposed therebetween, and heat of the semiconductor package 30 is efficiently radiated.
Here, the height of the male screw member 62, the length of the female screw member 61, the length of the coil spring 63 and the spring constant are previously determined, and the cooling unit 50 is pressed by the coil spring 63 with a predetermined constant pressing force.
FIG. 1 shows the conventional spring-pressurizing unit having the female screw member 61, the male screw member 62 and the coil spring 63.
Here, if the cooling unit 50 is mounted thereon and the female screw member 61 is screwed over the male screw member 62, the coil spring 63 gradually contracts in the screwing process, and the coil spring 63 presses the cooling unit 50.
Therefore, the female screw member 61 and the male screw member 62 are screwed with each other in a state where screw threads of the female screw member 61 and the male screw member 62 receive a strong force in a direction in which the coil spring 63 tries to extend, and the screw threads are shaved and metal powder is generated. If the female screw member 61 is rotated, the coil spring 63 is rotated due to the screwed state, an end of the coil spring 63 on the side of the base body 51 of the cooling unit 50 shaves the base body 51, and metal powder is generated. The metal powder may become a cause of accident of a short circuit of other circuit parts or wiring on the system board 10.
When the female screw member 61 is screwed over the male screw member 62 manually, since it is necessary to rotate the female screw member 61 against a force which is generated when the coil spring 63 contracts and which acts on the opposite direction, there is a problem that a burden on an arm of an operator is increased.
Here, patent document 1 relates to a direct-type valve gear in which a valve is directly pushed down and opened by rotation of a cam, and discloses a member for compressing a coil spring and a cam which pushes the member, but patent document 1 does not recognize the above problem and does not show solving means of the problem.    Patent Document 1: Japanese Patent Application Laid-open No. 11-148321